A woman cries as she walks past Philadelphia firefighters working on burned row homes on July 5, 2014, in Philadelphia. / Michael Perez, AP

by Yamiche Alcindor, USA TODAY

by Yamiche Alcindor, USA TODAY

Four children died early Saturday in a fast-moving fire that burned through a number of southwest Philadelphia row houses and displaced more than 40 people, according to several reports.

The dead children were not immediately identified, but officials told several reporters that they were in one home and included twin 4-year-old girls, a 4-year-old boy and a 1-month-old boy. Fire department officials said the blaze destroyed eight homes and engulfed at least 10 houses. Authorities are still investigating the cause of the fire, and a shelter for those displaced has been set up.

"This is a tragic, tragic day for the city of Philadelphia. Tragic," Philadelphia Fire Commissioner Derrick Sawyer told reporters. "We lost four children today. And I want everybody to understand that fire is everyone's fight. Not just the fire department. It's everyone's fight."

The fire started at about 2:40 a.m. Saturday, and was brought under control by about 4 a.m. The four children were pronounced dead at 5:10 a.m., according to Philly.com. Four people, including a woman and two 11-year-old girls, suffered minor injuries escaping the flames, the website said.

The mother of the twin girls killed in the fire managed to jump from a window and was treated for smoke inhalation, according to WPVI. She was taking care of the other children who died in the fire, the station reported.

A family friend, Jaka Kaba, told WPVI, "She's a mother everybody takes their children to her to take care of. There is nothing we can do. God knows why this happened."

The Red Cross, which is helping victims, says 42 people have been displaced by the fire, according to reports.

About 100 firefighters in 28 firetrucks responded to the blaze, Philly.com reports.

Philly.com also spoke with a man who told the website he saw the start of the blaze, called 911 and tried to get people out of their homes.

Jeff Boone, 27, told the website he was playing games on his PlayStation with his niece sleeping upstairs when he stepped outside his door and saw a couch on fire on the porch of a house about five doors down.

"As I seen the couch on fire, I ran back in my crib, grabbed my fire extinguisher," he said. But the extinguisher didn't work and the flames spread from porch to porch quickly.

"It looked like someone had a flamethrower and just shot it all across," he told Philly.com. "I was running, screaming, telling everybody, 'Get up! Yo, get yo! Go!'"

Other witnesses described their experiences.

"I was sleeping and I had seen the fire," Keisha Burgess, who lives on the block where the fire spread, told WCAU. "I just woke up and grabbed my kids. The fire was just spreading and it was just everywhere, house to house. I had to wake up, bring my kids out and just get out."

The television station also spoke with Karon Johnson, another resident and witness, who says the fire jumped from porch to porch, igniting everything in its path.

"It spread out from left to right so quickly," Johnson told WCAU. "When it all happened, I didn't know but somehow I hoped that everybody was OK and got out of the house. I didn't know who was safe and who wasn't."